1. Field of the Invention
The present invention relates to a radiation image storage panel employable in a radiation image recording and reproducing method utilizing a stimulable phosphor, and a process for the preparation of the same. 2. Description of Prior Arts
For obtaining a radiation image, there has been conventionally employed a radiography utilizing a combination of a radiographic film having a sensitive silver salt material layer and an intensifying screen.
As a method replacing the above-mentioned conventional radiography, a radiation image recording and reproducing method utilizing a stimulable phosphor as described, for instance, in U.S. Pat. No. 4,239,968, has been developed and paid much attention. The method involves steps of causing a stimulable phosphor to absorb a radiation having passed through an object or having radiated from an object; sequentially exciting (or scanning) the phosphor with an electromagnetic wave such as visible light or infrared rays (stimulating rays) to release the radiation energy stored in the phosphor as light emission (stimulated emission); photoelectrically detecting the emitted light to obtain electric signals; and reproducing the radiation image of the object as a visible image, numerals, symbols, etc. from the electric signals.
In the radiation image recording and reproducing method, a radiation image is obtainable with a sufficient amount of information by applying a radiation to the object at a considerably smaller dose, as compared with the conventional radiography. Accordingly, the radiation image recording and reproducing method is of great value, especially when the method is used for medical diagnosis.
In performing the radiation image recording and reproducing method, a stimulable phosphor is generally employed in the form of a radiation image storage panel having four sides (also referred to as stimulable phosphor sheet, and generally in the form of a sheet of rectangle, square, etc.) which comprises a support and a phosphor layer provided thereon. The phosphor layer comprises a stimulable phosphor and a binder. Further, a protective film made of a transparent plastic film is provided on a surface of the phosphor layer to protect the phosphor layer from physical and chemical deterioration.
The radiation image storage panel does not serve to finally record image information, but only stores the information temporarily to provide the image or the like on an independently prepared final recording medium as described above. Accordingly, the radiation image storage panel can be repeatedly used and such repeated use brings about economical advantage.
When a radiation image storage panel is repeatedly used, the panel is first subjected to a read-out process to recover the recorded radiation energy to obtain a desired image information and then subjected to a process for erasing the remaining radiation energy thereform in the manner as disclosed in Japanese Patent Provisional Publications No. 56(1981)-11392 and No. 56(1981)-12599. Thus, the radiation image storage panel is advantageously used repeatedly.
The radiation image storage panel can be repeatedly used in the following two representative processes. One process comprises use of a cassette for encasing the panel when the panel is transferred from the recording stage to the reproducing stages and vice verse. Another process comprises use of a endless conveying means for directly fixing the panel thereon and conveying it in cycle.
In the former process, the radiation image storage panel is repeatedly removed from and placed in the cassette by an operator, and is accordingly brought into physical contact with the side walls of the cassette. This physical contact causes physical deterioration of the panel. For obviating such contact and physical deterioration caused by the contact, the conventional radiation image storage panel is generally cut obliquely (i.e., chamferred) at the side edge.
The repeated use of the radiation image storage panel can be done, for instance, in the case that a radiation image information recording and reading device employing the radiation image storage panel is mounted on a traveling station such as a radiographic apparatuscarrying car to conduct mass radiographic examination in various places. In more detail, it is inconvenient to carry a great number of radiation image storage panels on a traveling station. Further, there is a limitation on the number of sheets capable of being carried on a car such as a radiographic apparatus-carrying car. Accordingly, it is practically useful that the radiation image storage panels are mounted on a radiographic car under such conditions that the radiation image storage panels are repeatedly used; radiation image information of an object is recorded on each radiation image storage panel and read out to obtain image information as a signal; and the obtained signal is transferred to a recording medium having a great recording capacity such as a magnetic tape so as to repeatedly use the radiation image storage panel in cycle. This means that radiation images of a number of objects can be obtained by use of a small number of radiation image storage panels. Further, the combination of the repeated use of the radiation image storage panels with a continuous radiographic process enables to perform rapid radiography in the mass radiographic examinations. This combination is of great value in practical use.
In the case that the device for recording and reading out the radiation image is carried on a traveling station such as a a radiographic apparatus-carrying car, the device is desirably mounted on the traveling station in the form of a united built-in device which comprises an image recording means for exposing a radiation image storage panel to a radiation having passed through an object so as to record and store a radiation image in the radiation image storage panel, a read-out means for reading out the radiation image stored in the radiation image storage panel, an erasure means for releasing and erasing radiation energy remaining in the radiation image storage panel for the next use of the radiation image storage panel, and a conveyance means for moving the radiation image storage panel in cycle to each of the aforementioned means. The radiation image information recording and reading device having the above-mentioned constitution have various advantages not only in mounting in the traveling station such as a radiographic apparatuscarrying car but also in setting in hospitals, so that the above device is convenient in practical use.
The above-mentioned device for recording and reading out radiation image information in which the radiation image storage panel is repeatedly employed in cycle is disclosed in Japanese Patent Application 58(1983)-66730 filed in the name of the present assignee, etc. Such device generally employs a radiation image storage panel-conveying system in which the panel is conveyed horizontally as well as conveyed vertically or nearly vertically in the device. The use of such combined conveying process is very advantageous to make the device compact.
In the conveying process comprising continuous movement of the radiation image storage panel in different directions, the front edge of the moving panel repeatedly strikes against a conveying roller, a conveying belt and the like. Such strike at the front edge likely causes physical deterioration or damage of the panel.
For obviating the physical deterioration of the moving radiation image storage panel caused by striking against the conveying members at the front edge, a number of measures have been thought. Such measures comprises provision of a reinforcing member to the front edge, coating the front edge with a resin, and inward retract of the phosphor layer on the support at the front edge. These measures have such disadvantage that additional processing of the radiation image storage panel is required.